The main source of oil leakage is found in the system for de-oiling the air from engine enclosures associated with the front and rear bearings of the engine: air flows to the bearing enclosures between parts that are rotary and stationary, and air picks up oil that is subsequently vented to the outside through a de-oiler system. Increasing the air/oil separation power of the de-oiler system makes it possible to reduce the oil consumption of the engine, or the turbojet, and thus reducing the operational cost.
Accompanying FIG. 1 shows an example of a known de-oiler system mounted in the rear bearing enclosure of a turbojet. This figure shows a rear bearing enclosure 10 and a hollow rotary shaft 12 (which also can be called “degassing shaft/tube” or “gas recovery shaft/tube”) for recovering gas that comes from a front bearing enclosure. It also shows pressurization tubes 14 that enable air to be injected into the enclosure 10 in order to prevent fluid entering into the enclosure.
De-oiling proper is obtained with the help of a centrifugal de-oiler 16 of annular shape that is mounted on the hollow rotary shaft 12. The inlet face 16a of the de-oiler 16 is in contact with the oil-laden air contained in the enclosure 10, while its outlet 16b communicates with the hollow rotary shaft 12. The centrifugal de-oiler 16 is constrained to rotate with the hollow rotary shaft 12. In simplified manner, the de-oiler 16 is constituted by a plurality of microchannels, e.g. constituted by a honeycomb structure, with the edges of the inlet face 16a tending, under the effect of the de-oiler rotating, to remove the oil droplets that are sent towards the enclosure 10 while allowing air to pass towards the hollow rotary shaft 12 under the effect of the pressure that exists in the enclosure 10. This thus separates the oil from the air, the oil being recovered by a pump circuit opening out into the bottom portion of the enclosure 10, which circuit is not shown in FIG. 1.
In such a system, the speed of rotation of the de-oiler 16 is naturally determined by the speed of rotation of the hollow rotary shaft 12. It is found that with such a system, the rate at which oil is separated from the air is significantly less than the target rate, and that this gives rise to increase oil consumption.